This invention relates in general to vehicle drive shaft assemblies and in particular to an improved structure and method for manufacturing a drive shaft assembly from a drive shaft tube formed from a composite material and an end fitting formed from a metallic material.
In many different types of vehicles, a drive shaft assembly is utilized to transmit rotational power from a source, such as an engine, to a driven component, such as a pair of wheels. A typical vehicle drive shaft assembly includes a hollow cylindrical drive shaft tube having an end fitting secured to each end thereof. Usually, the end fittings are embodied as end yokes which are adapted to cooperate with respective universal joints. For example, a drive shaft assembly of this general type is often used to provide a rotatable driving connection between the output shaft of a vehicle transmission and an input shaft of an axle assembly for rotatably driving the vehicle wheels.
In the past, both the cylindrical drive shaft tube and the two end fittings have been formed from a metallic material, such as steel. Steel end fittings are relatively easy to weld to a steel drive shaft tube, and the welded connection is effective for transmitting the torque loads normally encountered during vehicle use through the drive shaft assembly. However, such steel components are relatively heavy and, therefore, undesirably add weight of the vehicle. To address this, it is known to form the cylindrical drive shaft tube from a fiber reinforced composite material, such as carbon graphite or fiber glass reinforced synthetic resin. These composite materials are substantially lighter than steel, but still possess the strength and durability for transmitting the torque loads normally encountered during vehicle operation.
Unfortunately, because of the differences in the respective materials, it has been found to be somewhat difficult to provide a sufficiently strong connection between a drive shaft tube formed from a composite material and an end fitting formed from a metallic material. A number of structures and methods are known in the art for providing such a connection. For example, it is known to use an adhesive material to secure the metallic end fitting within the composite drive shaft tube. The use of adhesives alone, however, has not been found to be completely satisfactory. Alternatively, it is known to provide a tight friction engagement between the metallic end fitting and the composite drive shaft tube, and to reinforce this frictional engagement with a compression ring secured thereabout. While effective, this structure involves relatively tight tolerances and additional parts, increasing cost and complexity. Thus, it would be desirable to provide an improved structure and method for connecting a metallic end fitting to a composite drive shaft tube which is strong and durable, and which is relatively easy and inexpensive to construct.